After verbally sparring with Robert Downey Jr. in Jon Favreau’s Iron Man 2 and fending off invading aliens in Favreau’s upcoming Cowboys & Aliens, Sam Rockwell’s reward is a nice, quiet role in a dark comic thriller in which he gets to abuse prescription drugs and romance Jennifer Garner. That sounds like an upgrade.

Rockwell is negotiating to join Geoff Moore and David Posamentier’s Better Living Through Chemistry, Variety reports. He would replace a previously cast Jeremy Renner in the role of a meek, unhappy, small-town pharmacist who enters an illicit affair with a trophy wife (Garner) and begins to plot to murder her husband.

We knew Renner eventually had to let a few roles go. There’s only so much Renner to go around, and the Mission: Impossible co-star currently is attached to a Bourne reboot, a rally racing film, a potential Steve McQueen biopic, a new Ice Age movie, and who knows how many more projects.

Losing someone of Jeremy Renner's quality is rarely good for any production, but replacing him with the immensely gifted Rockwell is an excellent choice. I’m anxious to see Garner, who has been languishing in middling efforts like Arthur, Valentine’s Day and Ghosts of Girlfriend’s Past. She deserves better, and it’s starting to sound like Better Living could be it, especially since Moore and Posamentier, who will co-direct from their own script, and have already cast Michelle Monaghan as Rockwell’s wife and Judi Dench as the story’s narrator.